Calendar-based automatic reminding applications are well known in the art. They integrate a calendaring application, such as Microsoft Outlook Calendar, with a messaging application, such as Microsoft Exchange, to send electronic messages to a user informing him or her of a calendar entry (referred to herein as an appointment) at some selected period of time before the time of the appointment. An example thereof is MobiSMS from MobiMarketing, which synchronizes with Outlook Calendar to send short Message Service (SMS) calendar-entry reminders to communication devices of specified persons. The known applications send the reminders irrespective of other factors that may influence whether or not sending of the reminder is appropriate, such as the user's present activity, location, or direction of travel.
Location-based services, which assist people in their decision-making during performance of tasks in space and time, are also known. They support spatial queries, such as “the shortest route from here to there” and “nearest restaurant from here,” where “here” is the location of the user, specified either by the user or by any location-detecting system (e.g., Global Positioning Satellites, triangulation, etc.). Examples thereof are described in U.S. Pat. Nos. 5,963,861 and 6,177,905, and in M. Raubal and C. Rinner, “Multi-Criteria Decision Analysis for Location Based Services,” Proc. 12th Int. Conf. on Geoinformatics (Geoinformatics 2004) (Gavle, Sweden, 7-9 Jun. 2004), pp. 47-53. Another example is car or palmtop navigation tools that deliver a constant stream of instructions to the user based on the user's current location to help the user follow a route and arrive at a desired destination. Examples thereof are the CoPilot product of ALK Technologies Inc., the Destinator product of Homeland Security Technology Corporation, and a cell phone equipped with the Nokia Xpress-on GPS shell from Nokia Corporation.